Just looking at the tanks ignores the support and access areas around the tanks. Yes they wouldn't scale exactly linearly together but taking an existing farm a

Just looking at the tanks ignores the support and access areas around the tanks. Yes they wouldn't scale exactly linearly together but taking an existing farm and multiplying it up to get the capacity is better than just looking at the raw area taken up by the tanks. There's all sorts of pumping and piping that goes into these farms you'd have to route into the above ground mega tank farm version of the SPR. We're decades away from the point we could have even possibly built 100 miles squared of solar farm much less the batteries to store it and replacing all the uses of fossil fuel that aren't just electrical generators. Even if we snapped our fingers and magically replaced every extant car, plane, truck and train with an electric equivalent and had all the infrastructure there's still industrial uses of petroleum that would drive a desire for strategic reserves of the stuff.